计算有多少行具有相同的值，但如果 ID 不同，则将其分开

Question

Here's my query,

Select r.coupon_id,  c.who_added, c.coupon_name, r.when_added
From redeemed_coupons r 
JOIN coupon c on r.coupon_id = c.coupon_id AND c.who_added = 1 
AND r.when_added BETWEEN 1602827745 AND 1613084678 ORDER BY r.when_added 

How do I get the count of a row with same value of when_added but if the coupon_id is different you have to count it separately even if you have same when_added

the result go like this:

|coupon_id|who_added|coupon_name|when_added| total_count|
|---------|---------------------------------------------|
|    1    |    1    |Free Appe. |1602827745|      1     |
|    2    |    1    |Free Appe. |1602835586|      1     |
|    3    |    1    |10% off    |1603084636|      1     |
|    4    |    1    |50% off    |1603084678|      2     | 

Answer 1

Do you just want a count using a window function?

select r.coupon_id, c.who_added, c.coupon_name, r.when_added,
       count(*) over (partition by r.coupon_id, r.when_added) as cnt
from redeemed_coupons r join
     coupon c
     on r.coupon_id = c.coupon_id and
        c.who_added = 1 and
        r.when_added BETWEEN 1602827745 AND 1613084678
order by r.when_added ;

EDIT:

In older versions of MySQL, you can use a correlated subquery:

select r.coupon_id, c.who_added, c.coupon_name, r.when_added,
       (select count(*) 
        from redeemed_coupons r2 join
             coupon c2
             on r2.coupon_id = c2.coupon_id and
                c2.who_added = 1 and
                r2.when_added BETWEEN 1602827745 AND 1613084678
        where r2.when_added = r.when_added
      )
from redeemed_coupons r join
     coupon c
     on r.coupon_id = c.coupon_id and
        c.who_added = 1 and
        r.when_added BETWEEN 1602827745 AND 1613084678
order by r.when_added ;

Note that this is much less efficient than using window functions.